Well, I have good news to report. This morning I was able to get the engine to run through another 5 tanks of fuel (total of 6 now). It is definitely getting easier to start/run (although getting that first start took a bit of patience, every subsequent start was easy). I have the main needle still at 4 turns open and the idle a bit richer than it was before. It sounds a lot more stable than before - looks like just giving it time to run in was the trick.

It can happily run at the top end for as long as there's fuel now, and while half throttle still gets a little gurgly when the tank's more than 60% fuel (I think it's an issue with tank placement) it won't die on me if I carefully get back on the throttle (and don't keep it at half too long). Once fuel sits at 60% or below half thottle is no problem for any period of time. Very nice response and transition from that stage. I'm so relieved after this morning, to not have this engine constantly quitting on me or not even starting.

Patxipt, since it's just about an hour of rich running now, is this where you started closing the high speed? Can I ask how long it took you to reach 1 1/2 turns in? I am planning on adjusting the needle a bit (if the engine will take a leaner setting now) for the next trip out, and if it keeps running happily to take the plane up in the air to continue running it in there.

Any further advice?

Cheers, thanks to everyone for their input..

Ken